Disclaimer - There is a proper and accepted way to perform CYA testing that will maximize the accuracy for the home user. I am NOT questioning the need to properly test for CYA. But.....
There always seems to be a lot of fretting regarding performing the CYA test. Understanding the ideal way to perform the test is important for consistency, but at the end of the day, does the typical deviation for a home user really matter? As long as you perform the test outside, in natural light, does it actually matter if the dot is completely, 100% obscured, ghosted or not ghosted, etc - a somewhat subjective end point for the test? I am talking being close to the end-point for the test, not off by 40 ppm. What is the accuracy of the CYA turbidity test? I guess what I am asking is - if the test is performed under natural light, can that subjectivity really result in more than 10 ppm or so difference in accuracy. At the levels of CYA we generally recommend for a BBB pool, that really only means a difference of 2 ppm in the target FC for 30 vs 50 ppm CYA (10 high or 10 low from 40 ppm CYA), which in my mind is insignificant as I never let my FC approach the lower limit for sanitization.
I tried searching the internet for the accuracy of the test and came up empty handed.
There always seems to be a lot of fretting regarding performing the CYA test. Understanding the ideal way to perform the test is important for consistency, but at the end of the day, does the typical deviation for a home user really matter? As long as you perform the test outside, in natural light, does it actually matter if the dot is completely, 100% obscured, ghosted or not ghosted, etc - a somewhat subjective end point for the test? I am talking being close to the end-point for the test, not off by 40 ppm. What is the accuracy of the CYA turbidity test? I guess what I am asking is - if the test is performed under natural light, can that subjectivity really result in more than 10 ppm or so difference in accuracy. At the levels of CYA we generally recommend for a BBB pool, that really only means a difference of 2 ppm in the target FC for 30 vs 50 ppm CYA (10 high or 10 low from 40 ppm CYA), which in my mind is insignificant as I never let my FC approach the lower limit for sanitization.
I tried searching the internet for the accuracy of the test and came up empty handed.